Rough Comp of Horse and Rider cover picture

Here's a rough comp done in Photoshop of a new piece I'm working on.  I'm actually working on the acrylic painting right now.  Once again, it's a cover picture but not for any particular story.  She's some sort of Celtic-ish warrior woman I think.  I haven't done many horse pictures before, and I haven't done too many action pictures either so I thought I would try that.  I like horses in fantasy and mythology so I hope to put more in pictures in future.
  Speaking of horses, I was back in Upstate NY visiting my family over Christmas and I was able to do a little riding.  My cousin Sarah operates a horse stable and riding arena (handy!) so while I was there I got a chance to take one of her horses out for a spin.  I rode for quite a few years when I was younger.  I used to compete in English style and do some jumping.  But that was many years ago now.  I was so rusty and those muscles you need were really not there anymore.  I definitely enjoyed it--I was riding a beautiful and big horse named Paris--but I was very saddlesore for the next few days!